This is a competing continuation application, twice funded previously over the last ten years. The overall goal of this research is to: (i) develop novel monomer systems that will be more rapidly polymerizable, reach higher double bond conversions, display improved mechanical properties, and be subject to limited oxygen inhibition; (ii) synthesize monomers with novel allyl sulfide functional groups that form reversible crosslinks and enable significant stress relaxation during photo-polymerization; and (iii) develop a comprehensive understanding of the critical stress evolution that occurs in these and other photo-curing monomer systems (including currently used methacrylates), and use the chemistry developed in the first two Aims to create a functional polymeric system that can be employed in improved Dental restorative composite materials. This research has progressed significantly since the first funding cycle, and has resulted in numerous publications and patents. [unreadable] [unreadable]